1. Field of Invention
This invention relates to the use of chemical compositions to improve the performance of hydraulic cements, specifically the use of Boroncitrates to establish and control the time of set of hydraulic cements.
2. Prior Art
All hydraulic cement concrete, mortar and grouting placements do not take the same time to place and finish. Continuing the same method employed in making hydraulic cements in the early 1800's and regardless of changing needs, ninety percent of all hydraulic cements are manufactured with extended predetermined set times. Larger, more complex concrete structures require additional time to complete. Inversely, the need for faster setting, faster strength-gaining hydraulic cements for easy applications, or rapid retrofit construction, are now common necessities in all urban areas, and an absolute necessity for our military.
Unnecessary construction delays cost millions of dollars annually. In fact, the most costly waste during construction of structures requiring cementitious compositions is waiting for the concrete, mortar and grouts to take set—so they can begin to develop useable strengths.
Jobsite circumstances and the needs of those responsible for placing the materials would be better served if the set time could be slowed down or speeded up just before placement, as well as during placement. Without the ability to alter the time of set, to coincide with requirement for particular applications, cementitious compositions are provided which either stay plastic for hours or take set in minutes. This lack of flexibility insures job delays as every trade waits unnecessarily for slow setting concrete, mortar or grout to take set and start gaining strength, or relegates fast setting cements to small applications using small, less cost effective, mixing equipment.
As a result, owners, developers and contractors are becoming increasingly less satisfied with generic cements that take set slow and gain moderate strengths after days of waiting. In response to their customers dissatisfaction with the predetermined set times of their cement the portland cement manufactures have just recently reduced the set time of their cement from approximately six (6) hours to approximately five (5) hours. This modification acknowledges the problem but does not address the need for providing cements whose set time can be made either faster or slower as individual jobsite conditions dictate.